By virtue of the development of digital technologies and communication technologies, propagation and demand for audio/video centered multimedia content have remarkably expanded in various fields such as the Internet and personal media as well as broadcast and movie. In addition, consumer demand for immersive media for providing a three-dimensional effect through broadcasting and movies has increased. Along with propagation of a big TV screen at home in accordance with current trends as well as the development of display technologies, consumption for enjoying realistic contents with high image quality of high definition (HD) level or more. Immersive broadcast such as ultra high definition TV (UHDTV) as well as 3DTV has drawn attention as a next-generation broadcast service and, in particular, ultra high definition (UHD) broadcast services have been gradually discussed in accordance with current trends.
Currently, a broadcast subtitle service has been provided in the form of closed caption or digital video broadcasting (DVB) subtitle. Among these, in the case of DVB subtitle, a subtitle is provided in the form of a bitmap image and, thus, subtitles with different sizes are provided with respect to images with various sizes or a service needs to be provided by scaling a single type of subtitle. In the former case, efficiency may be lowered in terms of bandwidth and, in the latter case, sharpness may be lowered via scaling. In particular, recently, as a high resolution of broadcast service via UHDTV has been actively discussed, there is a need for a new broadcast subtitle service in order to overcome this problem.